A buck-boost converter is generally used in an electronic device to provide a stable output voltage while receiving an input voltage with wide range. The U.S. Pat. Nos. 6,166,527, 5,402,060 and 7,692,416 disclose the techniques about the buck-boost converter, however, in the buck-boost switching regulator disclosed by U.S. Pat. No. 6,166,527 and the buck-boost converter disclosed by U.S. Pat. No. 5,402,060, the switch connected to the output voltage cannot conduct both high voltage and low voltage (close to zero/ground), which may decrease the efficiency; and in the voltage up-and-down DC-DC converter disclosed by U.S. Pat. No. 7,692,416, two transistors of the transmission gate connected to the output voltage are controlled by the related signals in the buck mode and the boost mode, and the switching loss may be increased in this operation.
Therefore, how to provide a buck-boost converter which may have both better efficiency and lower switching loss is an important topic.